On hands 17 and 18 Michael and I had different ideas about which trump suit to choose. On the first hand we were Hinterhand and won the bidding at 20, and on the second we were Mittelhand and won it at 18 or 20. After the exchanges we had

Kiebitz tells me that on hand 18 you win your club game against any defence if you discard the spade and diamond queens, while Michael's spade game should be defeated rather easily.
On hand 17 both choices lose narrowly to best defence but are a little tricky to defeat.
It's reasonable that the short trump choice works better on hand 17 than hand 18, since you have more 'big ones'. Playing in clubs, if you discard S10 and DK you will be almost home if they let you trump (for example) the DA with your trump 10.